#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>
int main()
{
	int i = 0;
	double sum = 0;

	for (i = 1; i <= 100; i++)
	{
		int n = (-1);
		for (int j = 1; j <= i; j++)
		{
			n *= (-1);
		}
		sum += n * (1.0 / i);
	}
	printf("%lf\n", sum);

	return 0;
}